Articulating expandable intervertebral implant

ABSTRACT

A spacer for separating bones of a joint, the spacer includes a frame having a longitudinal axis, and ramped surfaces. An endplate configured to engage a bone of the joint has ramped surfaces mateable with the ramped surfaces of the frame. When the endplate is moved relative to the frame in a direction along the longitudinal axis of the frame, the endplate is moved in a direction away from the frame to increase the height of the spacer. A second endplate configured to engage a second bone of the joint can be similarly configured.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/963,720 filed on Jul. 30, 2015, which is a continuation-in-partapplication of U.S. patent application Ser. No. 13/782,724 filed on Mar.1, 2013, which is incorporated by its entirety herein.

FIELD OF THE INVENTION

This invention relates to stabilizing adjacent vertebrae of the spine byinserting an intervertebral spacer, and more particularly anintervertebral spacer that is adjustable in height.

BACKGROUND OF THE INVENTION

The vertebral or spinal column (spine, backbone) is a flexible assemblyof vertebrae stacked on top of each other extending from the skull tothe pelvic bone which acts to support the axial skeleton and to protectthe spinal cord and nerves. The vertebrae are anatomically organizedinto four generalized body regions identified as cervical, thoracic,lumbar, and sacral; the cervical region including the top of the spinebeginning in the skull, the thoracic region spanning the torso, thelumbar region spanning the lower back, and the sacral region includingthe base of the spine ending with connection to the pelvic bone. Withthe exception of the first two cervical vertebrae, cushion-like discsseparate adjacent vertebrae, i.e. intervertebral discs.

The stability of the vertebral column during compression and movement ismaintained by the intervertebral discs. Each disc includes a gel-likecenter surrounded by a fibrous ring. The gel-like center, i.e. nucleuspulposus, provides strength such that the disc can absorb and distributeexternal loads and contains a mixture of type II-collagen dispersed in aproteoglycan matrix. The fibrous ring, or annulus fibrosus, providesstability during motion and contains laminated rings of type-I collagen.Thus, the annulus fibrosis and the nucleus pulposus are interdependent,as the annulus fibrosis contains the nucleus pulposus in place and thenucleus pulposus aligns the annulus fibrosus to accept and distributeexternal loads. The integrity of the composition and structure of theintervertebral disc is necessary to maintain normal functioning of theintervertebral disc.

Many factors can adversely alter the composition and structure of theintevertebral disc, such as normal physiological aging, mechanicalinjury/trauma, and/or disease, resulting in impairment or loss of discfunction. For example, the content of proteoglycan in the nucleuspulposus declines with age, thus, it follows that the ability of thenucleus pulposus to absorb water concurrently declines. Therefore, innormal aging the disc progressively dehydrates, resulting in a decreasein disc height and possible de-lamination of the annulus fibrosus.Mechanical injury can tear the annulus fibrosis allowing the gel-likematerial of the nucleus pulposus to extrude into the spinal canal andcompress neural elements. Growth of a spinal tumor can impinge upon thevertebrae and/or disc potentially compressing nerves.

Bones of the spine, and bony structures, generally, are susceptible to avariety of weaknesses that can affect their ability to provide supportand structure. Weaknesses in bony structures have numerous potentialcauses, including degenerative diseases, tumors, fractures, anddislocations. Advances in medicine and engineering have provided doctorswith a plurality of devices and techniques for alleviating or curingthese weaknesses.

In some cases, the spinal column, in particular, requires additionalsupport in order to address such weaknesses. One technique for providingsupport is to insert a spacer between adjacent vertebrae.

SUMMARY OF THE INVENTION

In accordance with an embodiment of the disclosure, a spacer forseparating bones of a joint comprises a frame having a longitudinalaxis, and having at least one ramped surface; a first endplateconfigured to engage a first bone of the joint, and having at least oneramped surface mateable with the at least one ramped surface of theframe, whereby when the first endplate is moved relative to the frame ina direction along the frame longitudinal axis, the first endplate ismoved in a direction away from the frame to increase a height of thespacer; a second endplate configured to engage a second bone of thejoint; a link moveable with respect to the frame, the link having aprojection engageable with the first endplate to thereby move the firstendplate along the frame longitudinal axis when the link is moved withrespect to the frame; and an actuating screw moveable with respect tothe frame and pivotally connected to the link to cause movement of thelink when the actuating screw is moved with respect to the frame.

In various embodiments thereof, the spacer further includes a nutthreadably engaged with the actuating screw, the nut rotatable withrespect to the frame to move the actuating screw with respect to theframe; the nut is translatable along a predetermined path with respectto the frame; the spacer further includes an actuating support slideablyconnected to the frame to translate along a predetermined path withrespect to the frame, the actuating support rotatably supporting thenut; and the actuating support is slideably connected to the frame by aflanged connection; the spacer further includes a dovetailed connectionformed between the frame and the actuating support.

In a further embodiment thereof, the second endplate has at least oneramped surface mateable with the at least one ramped surface of theframe, whereby when the second endplate is moved relative to the framein a direction along the frame longitudinal axis, the second endplate ismoved in a direction away from the frame to increase a height of thespacer.

In yet further embodiments thereof, the actuating screw defines alongitudinal axis, the actuating screw pivotable in connection with thelink to form an angle between the actuating screw longitudinal axis andthe longitudinal axis of the frame; the link defines an elongated slot,and the actuating screw is pivotally connected to the link by a pinconnected to the actuating screw and projecting into the elongated slot;the endplate is curved along a substantial portion of its length; thenut is rotatable at a plurality of angular orientations between theactuating screw and the frame; and the first endplate and the frame forma sliding flanged connection therebetween.

In an additional embodiment thereof, the frame includes at least tworamped surfaces, and the first endplate includes at least one rampedsurface mateable with at least one of the at least two ramped surfacesof the frame, whereby when the endplate is slideably moved by rotationof the actuating screw and movement of the link, the at least one firstendplate ramped surface slides against the at least one frame rampedsurface to cause the first endplate to move along an axis transverse tothe longitudinal axis to increase a height of the spacer.

In alternative embodiments thereof, the first endplate includes one ormore projections configured to engage bone of the joint when the implantis positioned between bones of the joint; the actuating support includesa tool engagement connector configured to slidingly engage a tool end;the link defines an elongated slot, and the actuating screw is pivotallyconnected to the link by a pin connected to the actuating screw andprojecting into the elongated slot, and wherein as the actuating supporttranslates along the predetermined path, the pin translates within theelongated slot, and a height of the spacer is not thereby substantiallychanged; and the nut includes a circumferential groove, and theactuating support includes a circumferential groove, the spacer furtherincluding a ring configured to be positioned partially within both thenut groove and the actuating support groove, to rotatably retain the nutin connection with the actuating support.

In an alternative embodiment of the disclosure, a method of separatingbones of a joint comprises inserting a spacer between bones of thejoint, the spacer including—a frame having a longitudinal axis, andhaving at least one ramped surface; a first endplate configured toengage a first bone of the joint, and having at least one ramped surfacemateable with the at least one ramped surface of the frame, whereby whenthe first endplate is moved relative to the frame in a direction alongthe frame longitudinal axis, the first endplate is moved in a directionaway from the frame to increase a height of the spacer; a secondendplate configured to engage a second bone of the joint; a linkmoveable with respect to the frame, the link having a projectionengageable with the first endplate to thereby move the first endplatealong the frame longitudinal axis when the link is moved with respect tothe frame; and an actuating screw moveable with respect to the frame andpivotally connected to the link to cause movement of the link when theactuating screw is moved with respect to the frame.

In a further embodiment of the disclosure, a spacer for separating bonesof a joint comprises a frame having a longitudinal axis, and having atleast one ramped surface; a first endplate configured to engage a firstbone of the joint, and having at least one ramped surface mateable withthe at least one ramped surface of the frame, whereby when the firstendplate is moved relative to the frame in a direction along the framelongitudinal axis, the first endplate is moved in a direction away fromthe frame to increase a height of the spacer; a second endplateconfigured to engage a second bone of the joint; a link moveable withrespect to the frame, the link having a projection engageable with thefirst endplate to thereby move the first endplate along the framelongitudinal axis when the link is moved with respect to the frame; anactuating screw moveable with respect to the frame and pivotallyconnected to the link to cause movement of the link when the actuatingscrew is moved with respect to the frame; an actuating support slideablyconnected to the frame to be translatable along a predetermined path;and a nut rotatably connected to the actuating support, the nutthreadably mated to the actuating screw, whereby the nut is rotatable tomove the actuating screw and link to change a height of the spacer.

In an embodiment thereof, the link defines an elongated slot, and theactuating screw is pivotally connected to the link by a pin connected tothe actuating screw and projecting into the elongated slot, and whereinas the actuating support translates along the predetermined path, thepin translates within the elongated slot, and a height of the spacer isnot thereby substantially changed.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the disclosure, and the attendantadvantages and features thereof, will be more readily understood byreference to the following detailed description when considered inconjunction with the accompanying drawings, in which:

FIG. 1 is a perspective view of a spacer implant of the disclosure, withan articulating screw support;

FIG. 2 depicts a cross section of the spacer of FIG. 1, taken through anactuating screw of the spacer, with the screw support orientedlongitudinally, as further illustrated in FIGS. 4 and 5;

FIG. 3 depicts the cross section of FIG. 2, with the spacer expanded bya separation of endplates;

FIG. 4 depicts the spacer of FIG. 3, taken along an orientation 90degrees offset from the orientation of the spacer of FIG. 3;

FIG. 5 depicts the spacer of FIG. 2, taken along an orientation 90degrees offset from the orientation of the spacer of FIG. 2;

FIG. 6 depicts a cross section through the spacer of FIG. 1;

FIG. 7 depicts the spacer of FIG. 6, the endplates relatively separated;

FIG. 8 depicts a cross section of an alternative spacer of thedisclosure shown in FIG. 14, the endplates separated by pushing acarriage, having a screw support aligned with a longitudinal axis of thespacer;

FIG. 9 depicts the spacer of FIG. 8, the endplates separated;

FIG. 10 depicts the spacer of FIG. 8, taken along an orientation 90degrees offset from the orientation of the spacer of FIG. 8;

FIG. 11 depicts the spacer of FIG. 10, the endplates separated;

FIG. 12 depicts the spacer of FIG. 11, the screw support disposed at anangle with respect to the frame;

FIG. 13 depicts the spacer of FIG. 10, the screw support disposed at anangle with respect to the frame;

FIG. 14 is a perspective view of an alternative embodiment of a spacerof the disclosure, including a carriage which is pushed to separateendplates, and an actuator screw which is displaced within a screwsupport;

FIG. 15 depicts the spacer of FIG. 14, the endplates separated;

FIG. 16 is a perspective view of an alternative spacer embodiment of thedisclosure, having a curved shape;

FIG. 17 depicts a cross section of the spacer of FIG. 16, the endplatesnot separated;

FIG. 18 depicts a cross section of the spacer of FIG. 16;

FIG. 19 is a perspective view of an alternative spacer embodiment of thedisclosure, the actuating screw secured to the carriage by a nut;

FIG. 20 depicts a top view of the spacer of FIG. 19;

FIG. 21 is a cross section of the spacer of FIG. 19;

FIG. 22 is a perspective view of an alternative spacer embodiment of thedisclosure, having an articulating actuating mechanism, the spacer in anexpanded configuration;

FIG. 23 is an exploded view of the spacer of FIG. 22;

FIG. 24 illustrates the spacer of FIG. 22, in a contractedconfiguration, the actuating mechanism aligned with a longitudinal axisof the spacer;

FIG. 25 is a cross-sectional view of the spacer of FIG. 24, taken alonga central axis of the spacer;

FIG. 26 illustrates the spacer of FIG. 22, in an expanded configuration,the actuating mechanism angled with respect to a longitudinal axis ofthe spacer;

FIG. 27 is a cross-sectional view of the spacer of FIG. 26, taken alonga central axis of the spacer;

FIGS. 28-31 are alternative views of the actuating screw support of thespacer of FIG. 22;

FIGS. 32-33 are alternative views of the drive link of the spacer ofFIG. 22;

FIG. 34 is a perspective view of the frame of the spacer of FIG. 22; and

FIGS. 35-38 are alternative views of the nut of the spacer of FIG. 22.

DETAILED DESCRIPTION OF THE INVENTION

As required, detailed embodiments are disclosed herein; however, it isto be understood that the disclosed embodiments are merely examples andthat the systems and methods described below can be embodied in variousforms. Therefore, specific structural and functional details disclosedherein are not to be interpreted as limiting, but merely as a basis forthe claims and as a representative basis for teaching one skilled in theart to variously employ the present subject matter in virtually anyappropriately detailed structure and function. Further, the terms andphrases used herein are not intended to be limiting, but rather, toprovide an understandable description of the concepts.

The terms “a” or “an”, as used herein, are defined as one or more thanone. The term plurality, as used herein, is defined as two or more thantwo. The term another, as used herein, is defined as at least a secondor more. The terms “including” and “having,” as used herein, are definedas comprising (i.e., open language).

With reference to FIGS. 1-3, the disclosure provides an expandablespacer 100 having an adjustable height. The implant is inserted betweentwo adjacent bony surfaces to facilitate separation of the bones, and ifdesired, to promote the fusion of bony surfaces. Although intended to beuseful with any adjacent bony surface in which fusion is desired, theimplant is advantageously applied to insertion between two adjacentvertebral bodies in any section of the spine, including the cervical,thoracic, lumbar, and sacral vertebral sections. More than one spacer100 may be implanted within the body, for example between successive orseparated vertebrae, between adjacent vertebrae. The use of multipleimplants is particularly advantageous for patients whose back pain isnot limited to a localized area, or for patients whose localized damagehas progressed to other areas of the spine.

The implant and methods for its insertion can be used in a treatmentprotocol for any of a wide variety of conditions in a patient involvingdiseased or damaged bony structures. The patient can be a human being.Additionally, it is contemplated that the implant may be useful inveterinary science for any animal having adjacent bony structures to befused. The implant can collapse, for example, to approximately one halfof an expanded size. When in this collapsed configuration, the implantcan be inserted into a space through a small incision and narrowpathways, using appropriate minimally-invasive techniques, and can bepositioned within the space between adjacent bones, and there expandedto a desired therapeutic height. The incision may be short, for exampleabout one inch in length, which is smaller than the implant in anexpanded configuration. If the desired position and/or expansion are notachieved, the implant can be collapsed, repositioned, and re-expanded insitu.

Although the implant is exemplified herein for use in the spine, theimplant is contemplated for fusion of any bony structures. While theimplants are described herein using several varying embodiments, theimplants are not limited to these embodiments. An element of oneembodiment may be used in another embodiment, or an embodiment may notinclude all described elements.

With reference to FIGS. 1-5, a spacer 100 of the disclosure includesendplates 102, 104 having expansion ramps 150, mateable with moveablelift ramps 250 of a carriage 200. In the embodiment shown, endplates102, 104 are symmetrical, and spacer 100 can be implanted with eitherendplate positioned superior with respect to the other. In otherembodiments, they may be dissimilar, and a particular orientation maythen be advantageous or necessary.

Spacer 100 forms a distal end 154 which is inserted first into the body,and which can be tapered to facilitate insertion between body tissue,and a proximal end 156, to which a tool may be connected. Distal andproximal ends 154 and 156 define a longitudinal axis 158, extendingtherebetween. To expand Spacer 100, lift ramps 250 are displacedrelative to endplates 102, 104, causing expansion ramps 150 to slidealong lift ramps 250, thereby moving endplates 102, 104 relativelyapart, thereby increasing a height of Spacer 100. Body tissue engagingprojections 152, for example tooth shaped projections, can be providedupon a surface of endplate 102, 104, to further secure spacer 100 in atherapeutic location.

Lift ramps 250 extend from carriage 200, which is slideably retainedwithin a frame 126 extending between endplates 102, 104. Carriage 200 isdisplaced relative to endplates 102, 104 by being pulled by a pin 106connected to a link 108 threadably connected to an actuating screw 110.One or more guide elements 112, associated with frame 126, can beprovided to prevent endplates 102, 104 from moving along longitudinalaxis 158 along with carriage 200, thereby causing lift ramps 250 andexpansion ramps 150 to be moved relative to each other, expanding orcontracting Spacer 100. Actuating screw can be prevented from movingalong longitudinal axis by a blocking flange 114 or 174.

With further reference to FIGS. 6-7, in accordance with the disclosure,an articulating screw support 160 is slideably retained in connectionwith frame 126 by, in one embodiment, a flanged connection 162. In thismanner, a longitudinal axis 168, defined by screw support 160, may forma changeable angle (α) with respect to longitudinal axis 158 ofendplates 102, 104, or a longitudinal axis of frame 126. Actuating screwis rotatably confined within screw support 160, and is threadablyengaged with link 108. Pin 106 pivotally retains link 108 in connectionwith carriage 200. A slot 202, associated with carriage 200, enablesmovement of pin 106, whereby pin 106 and link 108 can maintain a fixedorientation with respect to screw support 160, regardless of an angulardisposition of screw support 160. Slot 202 is thus configured anddimensioned to enable a location of pin 106, confined therewithin, tocorrespond to a path of travel of screw support 160 as defined byconnection 162.

In one embodiment, a path of travel of screw support 160 is defined byconnection 162 to maintain a fixed orientation of carriage 200 withrespect to frame 126. More particularly, if screw support 160 is movedalong a path which does not pivot about a single point defined by acurrent location of pin 106, pin 106 may move within slot 202 tomaintain a fixed distance in a contracted position between pin 106 andscrew support 160, and therefore carriage 200 is not caused to be movedas screw support 160 is moved. In other embodiments, slot 202 is definedto cause a predetermined movement of carriage 200 as screw support 160is moved.

Similarly, regardless of a given orientation of screw support 160,rotation of actuating screw advances or retards link 108 and pin 106,causing movement of carriage 200 relative to endplates 102, 104. Moreparticularly, slot 202 defines a longitudinal axis 268, which isoriented to lie at a non-perpendicular angle (β) with respect tolongitudinal axis 168 of screw support 160, through a substantialportion of the range of motion of screw support 160. In this manner,once a desired orientation of screw support 160 has been established,rotation of actuating screw 110 causes pin 106 to push or pull along anedge of slot 202, thereby causing movement of carriage 200. If axis 168and 268 are perfectly perpendicular, it is possible no movement can becaused by threading screw 110; however, as a practical matter,reorienting screw support 160 a very small amount can resolve thistheoretical limitation. Carriage 200 is slideably retained by a channelor edge interface 116 formed between carriage 200 and at least oneendplate 102, 104, thereby limiting movement of carriage 200 alonglongitudinal axis 158.

With reference to FIGS. 8-15, an alternative spacer 100A of thedisclosure functions in analogous manner to the embodiment of FIGS. 1-7,however in this embodiment, rotation of actuating screw 110A causescarriage 200A to push endplates 102A, 104A to cause expansion. Moreparticularly, an orientation of expansion ramps 150A and lift ramps 250Aare oriented 180 degrees with respect to longitudinal axis 158. Theembodiment of FIGS. 8-9 additionally illustrates an alternativeactuating screw 110A configuration, in which screw 110A is rotatablyconnected to link 108A, and threadably connected within screw support160A, whereby screw 110A moves along longitudinal axis 168 within athreaded bore 118A of screw support 160A. Screw 110A causes movement oflink 108A, which advances or retards pin 106 within slot 202, to cause acorresponding movement of carriage 200A. As the various aspects ofdiffering embodiments of the disclosure may be substituted wherelogical, generally, it may be seen that this alternative screw 110Aconfiguration can be used with other embodiments of the disclosure, aswell.

As may be seen in FIG. 2, for example, in one embodiment, connection 162includes interlocking mating flanges 164, 166, associated with frame 126and screw support 160, respectively. Flanges 164, 166 form mutuallycurved guide surfaces defining a path of movement for screw support 160relative to frame 126, and retain screw support 160 in engagement withframe 126. Other configurations are possible, provided screw support 160and frame 126 may form different angular dispositions with respect toeach other, and wherein actuating screw 110 or 110A (FIG. 8) mayinteract with carriage 200 or 200A to slide carriage 200 or 200A withrespect to frame 126, 126A.

Turning now to FIGS. 16-18, spacer 100B includes curved endplates 102B,104B, and a curved carriage 200B slideable within edge interface 116B.Carriage 200B includes a threaded bore 218, into which actuating screw110B is threaded. As screw 110B is rotated in a first direction,carriage 200B is moved towards distal end 154, and as screw 110B isrotated in a second, opposite direction, carriage 200B is moved awayfrom distal end 154. Depending upon the angular direction of ramps 150Band 250B, endplates 102B, 104B are moved together or apart, as describedwith respect to the embodiments of FIGS. 1 and 8. Spacer 100B forms,overall, a curved shape, which can advantageously be rotated as it isinserted through a minimal incision, to thereby become implanted betweenadjacent bones. This reduces an extent of a requirement of rotating aspacer, within the body, prior to insertion between the bones, thusreducing an adverse impact to adjacent body tissue.

As actuating screw 110B threads into carriage 200B, shaft 140 and head142 of screw 110B are angularly displaced with respect to screw support160B. accordingly, screw support 160B is provided with a gapped region170, allowing movement of screw 110B. Additionally, screw support 160Bis retained in connection with a frame 126B by a flanged connection162B, in this case a dovetail connection. Connection 162B enables screwsupport 160B to be angled with respect to frame 126B, to facilitateaccess to screw 110B by a tool (not shown), when spacer 100B isimplanted within the body, and to further enable screw 110B to change anangle with respect to frame 126B.

Frame 126B is connected to each of endplates 102B, 104B by a flangedconnector 176, in this embodiment a dovetail formed between endplateflanges 178 extending from each of endplates 102B, 104B, and frameflanges 180 associated with an intermediate connector 182. Actuatingscrew 110B can be rotatably retained within screw support 160B by awasher or flange (not shown) positioned in groove 186 within screwsupport 160B, or intermediate connector 182 can be configured torotatably retain screw 100B.

With reference to FIGS. 16-18, a spacer 100C functions in a similarmanner to spacers 100, 100A, and 100B, with the following distinctions.Initially, in the embodiment shown, screw support 160C does not slidealong a flanged connector 162, and is connected to endplates 102C, 104Cin a like manner as spacer 100B. However, screw support 160C could beconnected to a remainder of spacer 100C using a flange connector 162.Additionally, actuating screw 110C has a tool engagement 188C that isdifferent than the tool engagement of other embodiments, althoughengagement style 188, or any other style tool engagement, may beprovided upon screw 110C. Engagement style 188 allows for articulatingbetween the holder and the implant by pivot point 192.

As may best be seen in FIGS. 20 and 21, nut 198 retains actuating screw110C in connection with carriage 200C. However, in distinction withrespect to threaded bore 218 of spacer 100B, nut 198 may toggle, orchange an angular orientation with respect to carriage 200C, as screw100C is rotated, and carriage 200C is moved. Nut 198 can be providedwith a nut bearing surface 198′, which mateably interacts with acarriage bearing surface 208. Similar bearing surfaces 198″ and 208′ canbe provided on an opposite side of nut 198, for pushing carriage 200C inan opposite direction. In the embodiment shown, threading nut 198 in thedirection of proximal end 156 causes an expansion or increase in heightof spacer 100C, and threading nut 198 in a direction of distal end 154causes a reduction, or decrease in height of spacer 100C. However, ramps150C and 250C can be oriented to cause an opposite effect.

The following discussion pertains to all embodiments of the disclosure,including spacers 100, 100A, 100B, 100C, and 100D. For brevity, theletter suffix designating variations of like parts will be omitted,unless a specific distinction is made. For all spacer 100 embodiments ofthe disclosure, carriage 200 can be slid, or actuated, when screwsupport 60 is disposed at an angle with respect to the carriage. In theembodiments of FIGS. 1-15, this angle may vary between 0° and 70°, andwith modifications, this angle could be increased to a theoreticalmaximum approaching 180°. The embodiment of FIGS. 16-18 accomplishesdisposing screw 100B at an angle to the endplate bodies by curving theendplates, and by configuring bore 218 at an angle with respect tocarriage 200B.

In all embodiments, head 142 of screw 110 may be accessed by a drivingtool extending from outside the body, into the body, while endplates102, 104 lie at an angle, for example perpendicular, to a pathway intothe body. More particularly, spacers 100 of the disclosure may beinserted between vertebral bodies when in a collapsed or non-expandedstate, from a lateral approach to the spine. As spacer 100 is insertedbetween endplates, it is rotated to contact cortical bone of theendplates, and to avoid anatomical structures which should not bedisturbed.

Once rotated into position, screw support 60 can be turned towards anexterior of the body, if it has not already been so turned, whereby atool may be conveniently mated with a tool engagement 188 of screw head142. After screw 110 is rotated, endplates 102, 104 separate, expandingor increasing a height of spacer 100, and restoring and maintaining atherapeutic spacing between adjacent bones. In some embodiments, afterexpansion of spacer 100, screw support 160 may slid along flangedconnection 162 to lie at an optimal orientation with respect to bodytissue, for example 0 degrees with respect to carriage 200, or at anangle deemed best by the medical practitioner.

Spacers 100 may include ramps 150, 250 of differing height within aspacer, whereby endplates 102, 104 mutually separate at different ratesat distal and proximal ends 154, 156, or at sides transverse to distaland proximal ends 154, 156, whereby an angular disposition of adjacentbones may be changed, for example to correct lordosis or scoliosis.Endplates 102, 104 may additionally, or alternatively, be resilient, sothat they may conform to bony surfaces, forming a more stable supportplatform. Accordingly, endplates 102, 104 can be fabricated from apolymeric material, a naturally resilient material, or a resilientmetal, for example a shape memory alloy, or any other resilientbiocompatible material of sufficient strength and durability forseparating bones within the body. Spacers 100 may further be removed orrepositioned during an initial implantation procedure, or later in time.

Referring now to FIGS. 22-38, in an alternative embodiment, in whichlike numbers correspond to like elements in other embodiments herein, aspacer 100D of the disclosure includes a frame 126D having lift ramps250D slidingly engageable with expansion ramps 150D of endplates 102D,104D. Drive link 120 is engaged with endplates 102D, 104D, and isconfigured to pull and displace endplates 102D, 104D with respect toframe 126D, to thereby cause expansion ramps 150D to slide along liftramps 250D. Accordingly, endplates 102D, 104D move relatively apartalong an axis which is transverse to longitudinal axis 158, to increasea height of spacer 100D. In this embodiment, spacer 100D does notinclude a carriage 200 which is displaced with respect to a frame 126,as is disclosed elsewhere herein, but rather displaces endplates 102D,104D with respect to a ramped frame 126D. Arrow “A” indicates anorientation of link 120 with respect to endplate 102D, and arrow “B”indicates an orientation of link 120 with respect to frame 126D.

As may be seen in the embodiment of spacer 100D, and other embodimentsherein, expansion ramp 250D includes a sliding flanged connectionincluding a side projecting edge 254D which engages a mating channel 306within endplate 102D or 104D. In this manner, endplates 102D, 104D areretained in connection with frame 126D throughout an extent ofseparation of endplates 102D, 104D. It should be understood, however,that the endplate 102D or 104D can include a side projecting edge 254D,and the frame can include a channel 306.

Link 120 includes endplate engaging projections 134, 136 which engagecorresponding openings 302, 304 in endplates 102D, 104D, respectively.Endplate engaging projections 134, 136 pass through a central opening190, thereby enabling link 120 to move along axis 158, which axis may benon-linear for curved embodiments, including spacer 100D. In theembodiment shown, link 120 pulls endplates 102D, 104D to expand spacer100D; however, it should be understood that link 120 could alternativelyoperate to expand spacer 100D by pushing endplates 102D, 104D, forexample if ramps 150, 250D had reversed angles, and projections 134, 136positively engaged endplates 102D, 104D along axis 158.

Link 120 and endplates 102D, 104D move together with respect to frame126D, as spacer 100D is expanded or contracted. Link 120 is pivotallyengaged with an actuating screw having the form of a threaded clevislink 108D, to pivot about an axis 270 extending from endplate 102D toendplate 104D, and substantially perpendicular to longitudinal axis 158.Pin 106D passes through slot 202D in link 120. In the embodiment shownin FIG. 23, pin 106D is provided in segments, but could alternatively bea unitary pin.

Nut 280 includes internal threads 282 which mate with external threads284 of link 108D. Nut 280 is rotatably retained in fixed axialorientation within articulating screw support 160D. In an embodiment, acompressible ring 286 (visible in FIGS. 25 and 27), is positioned inpart within a channel 288 within nut 280, and in part within a channel290 within support 160D. Nut 282 includes tool engaging portions 292sized and dimensioned to cooperate with a tool (not shown) configured tomate to engaging portions and rotate nut 280 with respect to link 108D,which is prevented from rotation through connection with link 120.Accordingly, as nut 282 is rotated, link 108D is advanced or withdrawnwith respect to frame 126D.

Articulating screw support 160D slideably attaches to frame 126D througha curved flanged or dovetail connection 294, which is formed betweensupport dovetail portion 296, and frame 126D dovetail portion 298. Thecurved connection enables support 160D to be positioned for actuation ofnut 280 at an angle with respect to a longitudinal axis of spacer 100D.In this manner, spacer 100D may be inserted into the body along anon-linear path, for example during a transforaminal, posterior, and/orlateral insertion, and support 160D may be positioned to be more readilyaccessible along the insertion path to a tool end which engages nut 282for rotation, thereby minimizing disturbance of body tissue. Arrow “C”indicates an orientation of link 108D with respect to frame 126D, andarrow “D” indicates an orientation of link 108D with respect to support160D.

In addition, slot 202D enables actuating support 160D to be translatedalong a path defined by dovetail portion 298, without substantiallychanging a height of spacer 100D. More particularly, a change inlocation of link 108D due to translation along the path does not causemovement of endplates 102D, 104D, because pin 106D may translate orpivot within slot 202D, thereby not causing movement of link 108D.However, in any position of actuating support 160D along the path, nut280 may be rotated to displace link 108D, regardless of a location ofpin 106D, to change a height of spacer 100D.

Once support 160D is positioned angularly, dovetail connection 294secures support 160D with respect to frame 126D, whereby rotation of nut280 causes links 108D and 120 to move with respect to frame 126D,thereby moving endplates 102D, 104D with respect to frame, causing anexpansion or contraction of a height of spacer 100D.

Articulating screw support 160D further includes a tool engagingconnector 300 sized and dimensioned to slidingly engage a mating toolend (not shown). In the embodiment shown, connector 300 is a dovetailedconnector, although other tool engagement types or shapes can be used,as would be understood within the art. In this manner, spacer 100D maybe manipulated into position within the body, and support 160D may bemoved to be disposed at a desired angle with respect to an entry path ofspacer 100D into the body.

Spacer 100D, as well as other spacer embodiments of the disclosure, canbe inserted at a contracted height transforaminally, for example, andare capable of articulating into anterior placement. Once placement isachieved, the implant is capable of expanding for disc heightrestoration. Additionally, the implant can be positioned anteriorly, andcan be expanded through a continuous range to provide axial balance andgreater endplate contact area. Additionally, spacers of the disclosureallow for superior sagittal correction, through the use of a relativelysmaller insertion window, decreasing the need for boney damage. Thus,spacers of the disclosure provide the benefits of an ALIF device througha familiar posterior approach, decreasing surgery time and associatedblood loss, as well as eliminating the need for an access surgeon.

With respect to all embodiments, in accordance with the disclosure,during implantation of intervertebral spacers from a posterior approach,there is a need to avoid damaging nerve roots. A prior art spacerdimensioned to separate bones can block a view of nerve roots as it isinserted, and due to its large size, poses a greater risk of contactingnerve roots during insertion into the body. As a result, the medicalpractitioner must more often retract nerve roots, with attendant dangerof tissue damage. Spacers 100 of the disclosure form a smaller dimensionduring implantation, relative to a final dimension for spacing bones.Accordingly, nerve roots can be visualized and avoided during insertion,and nerve root manipulation can be avoided or minimized.

As spacers 100 of the disclosure can be articulated during implantation,they can be inserted between bones by being passed through a minimallyinvasive entry, for example through an incision approximating thesmallest collapsed dimension, for example transverse to a longitudinaldimension extending between distal and proximal ends 154, 156. Thisenables exceptional anterior placement without impaction, as well asfacilitating implantation from other approaches. Implants of thedisclosure further develop a good bone contact area, as an implant witha larger footprint may be inserted through a reduced size incision, dueto the overall dimensions of the implant being reduced during insertion.

Spacers 100 of the disclosure enable a continuous expansion andretraction over a range of displacements according to predetermineddimensions of a specific spacer design. This provides the ability todistract vertebral bodies or other bones to a desired height orseparation. Endplates 102, 104 can be shaped to form planes or surfaceswhich converge relative to each, to provide for proper lordosis, and canbe provided with openings 190 through which bone may grow, and intowhich bone graft material may be placed. Spacers 100 of the disclosuremay be used to distract, or force bones of a joint apart, or may be usedto maintain a separation of bones created by other means, for example bya retractor. Endplates may additionally be curved to conform to thesurface of body tissue, for example the surface of cortical bone, of thevertebra to be contacted, for improved fixation and load bearing.

Spacers 100 of the disclosure may be further secured in connection withthe body by passage of elongated fasteners through frame 162, or anendplate 102, 104. As described therein, a blocking mechanism can beused to prevent backing out of the elongated fastener. Similarly, screw110 can be provided with a blocking mechanism as described in theforegoing reference, or a resilient washer (not shown) may be positionedwithin groove 186, to resist unintended rotation of screw 110.

Implants of the disclosure may be fabricated using any biocompatiblematerials known or hereinafter discovered, having sufficient strength,flexibility, resiliency, and durability for the patient, and for theterm during which the device is to be implanted. Examples include butare not limited to metal, such as, for example titanium and chromiumalloys; stainless steel, polymers, including for example, PEEK or highmolecular weight polyethylene (HMWPE); and ceramics. There are manyother biocompatible materials which may be used, including otherplastics and metals, as well as fabrication using living or preservedtissue, including autograft, allograft, and xenograft material.

Portions or all of the implant may be radiopaque or radiolucent, ormaterials having such properties may be added or incorporated into theimplant to improve imaging of the device during and after implantation.

Spacers 100 may be formed using titanium, or a cobalt-chrome-molybdenumalloy, Co—Cr—Mo, for example as specified in ASTM F1537 (and ISO5832-12). The smooth surfaces may be plasma sprayed with commerciallypure titanium, as specified in ASTM F1580, F1978, F1147 and C-633 (andISO 5832-2). Alternatively, part or all of spacers 100 may be formedwith a polymer, for example ultra-high molecular weight polyethylene,UHMWPE, for example as specified in ASTM F648 (and ISO 5834-2). In oneembodiment, PEEK-OPTIMA (a trademark of Invibio Ltd Corp, UnitedKingdom) may be used for one or more components of the implants of thedisclosure. For example, polymeric portions can be formed withPEEK-OPTIMA, which is radiolucent, whereby bony ingrowth may beobserved. Other polymeric materials with suitable flexibility,durability, and biocompatibility may also be used.

In accordance with the invention, implants of various sizes may beprovided to best fit the anatomy of the patient. Components of matchingor divergent sizes may be assembled during the implantation procedure bya medical practitioner as best meets the therapeutic needs of thepatient, the assembly inserted within the body using an insertion tool.Implants of the invention may also be provided with an overall angulargeometry, for example an angular mating disposition of endplates, toprovide for a natural lordosis, or a corrective lordosis, for example offrom 0° to 12° for a cervical application, although much differentvalues may be advantageous for other joints. Lordotic angles may also beformed by shaping one or both endplates to have relatively non-coplanarsurfaces.

Expanded implant heights, for use in the cervical vertebrae for example,may typically range from 7 mm to 12 mm, but may be larger or smaller,including as small as 5 mm, and as large as 16 mm, although the size isdependent on the patient, and the joint into which an implant of theinvention is to be implanted. Spacers 100 may be implanted within anylevel of the spine, and may also be implanted in other joints of thebody, including joints of the hand, wrist, elbow, shoulder, hip, knee,ankle, or foot.

In accordance with the invention, a single spacer 100 may be used, toprovide stabilization for a weakened joint or joint portion.Alternatively, a combination of two, three, or more of any of spacer 100may be used, at a single joint level, or in multiple joints. Moreover,implants of the disclosure may be combined with other stabilizing means.

Additionally, spacers 100 of the disclosure may be fabricated usingmaterial that biodegrades in the body during a therapeuticallyadvantageous time interval, for example after sufficient bone ingrowthhas taken place. Further, implants of the disclosure are advantageouslyprovided with smooth and or rounded exterior surfaces, which reduce apotential for deleterious mechanical effects on neighboring tissues.

Any surface or component of an implant of the disclosure may be coatedwith or impregnated with therapeutic agents, including bone growth,healing, antimicrobial, or drug materials, which may be released at atherapeutic rate, using methods known to those skilled in the art.

Devices of the disclosure provide for adjacent vertebrae to be supportedduring flexion/extension, lateral bending, and axial rotation. In oneembodiment, spacer 100 is indicated for spinal arthroplasty in treatingskeletally mature patients with degenerative disc disease, primary orrecurrent disc herniation, spinal stenosis, or spondylosis in thelumbosacral spine (LI-SI). Degenerative disc disease is advantageouslydefined as discogenic back pain with degeneration of the disc confirmedby patient history and radiographic studies, with or without leg(radicular) pain. Patients are advantageously treated, for example, whomay have spondylolisthesis up to Grade 1 at the involved level. Thesurgery position spacer 100 may be performed through an Anterior,Anterolateral, Posterolateral, Lateral, or any other approach.

In a typical embodiment, spacer implants of the disclosure have anuncompressed height, before insertion, of 7 to 13 mm, and mayadvantageously be provided in cross-sections of 10×26 mm, 12×31 mm and12×36 mm, with 4, 8, 12, or 16 degree lordotic angles, although theseare only representative sizes, and substantially smaller or larger sizescan be therapeutically beneficial. In one embodiment implants inaccordance with the instant disclosure are sized to be inserted using anMIS approach, for example using a reduced incision size, for exampleless than about 5 cm, and advantageously less than about 2.5 cm, withfewer and shorter cuts through body tissue. Spacer 100 mayadvantageously be used in combination with other known or hereinafterdeveloped forms of stabilization or fixation, including for example rodsand plates.

Spacer implants of the disclosure can be inserted into the body,advantageously in a contracted or non-expanded configuration, through atransforaminal approach, and can articulate in attachment to an insertertool (not shown), for example for anterior placement. Once placement isachieved, the implant is capable of expanding for disc heightrestoration. To maintain an engagement spacer 100 and an insertion tool,a driving end (not shown) of the tool is inserted into tool engagement188. To prevent separation of the tool and spacer 100, a tool connector192 may be provided, extending from or formed within screw support 60.In the embodiment shown in FIG. 16, for example, tool connector 192extends from a surface of screw support 60B, and is releaseably graspedby a mating tool portion.

Portions of spacer 100 may be radiopaque or radiotransparent. To improvevisibility under imaging, radiopaque elements 194 may be provided inpredetermined locations within spacer 100. In the embodiment of FIG. 16,for example, elements 194 are positioned within at least one of endplate102B, 104B.

Implant spacers 100 of the disclosure can be positioned anterioriorlyand continuously expanded to provide axial balance and greater endplatecontact area, and allow for superior sagittal correction, and areinsertable into the body through a smaller window, decreasing the needfor damage and trauma to body tissue. Spacers 100 of disclosure providethe benefits of an ALIF device, implantable through a familiar posteriorapproach, decreasing surgery time and associated blood loss, as well aseliminating the need for an access surgeon.

All references cited herein are expressly incorporated by reference intheir entirety. There are many different features to the presentinvention and it is contemplated that these features may be usedtogether or separately. Unless mention was made above to the contrary,it should be noted that all of the accompanying drawings are not toscale. Thus, the invention should not be limited to any particularcombination of features or to a particular application of the invention.Further, it should be understood that variations and modificationswithin the spirit and scope of the invention might occur to thoseskilled in the art to which the invention pertains. Accordingly, allexpedient modifications readily attainable by one versed in the art fromthe disclosure set forth herein that are within the scope and spirit ofthe present invention are to be included as further embodiments of thepresent invention.

What is claimed is:
 1. A spacer for separating bones of a joint, thespacer comprising: a frame having a longitudinal axis and at least oneramped surface; a first endplate configured to engage a first bone ofthe joint, the first endplate having at least one ramped surfacemateable with the at least one ramped surface of the frame, whereby whenthe first endplate is moved relative to the frame in a direction alongthe frame longitudinal axis, the first endplate is moved in a directionaway from the frame to increase a height of the spacer; a secondendplate configured to engage a second bone of the joint; a linkmoveable with respect to the frame, the link engageable with the firstendplate to thereby move the first endplate when the link is moved withrespect to the frame; an actuating screw moveable with respect to theframe and coupled to the link to cause movement of the link when theactuating screw is moved with respect to the frame; and a nut engagedwith the actuating screw, the nut rotatable with respect to the frame tomove the actuating screw with respect to the frame.
 2. The spacer ofclaim 1, wherein the nut is translatable along a predetermined path withrespect to the frame.
 3. The spacer of claim 1, further including anactuating support slideably connected to the frame to move along apredetermined path with respect to the frame, the actuating supportrotatably supporting the nut.
 4. The spacer of claim 3, wherein theactuating support is slideably connected to the frame by a flangedconnection.
 5. The spacer of claim 3, further including a dovetailedconnection formed between the frame and the actuating support.
 6. Thespacer of claim 3, wherein the actuating support includes a toolengagement connector configured to slidingly engage a tool end.
 7. Thespacer of claim 3, wherein the link defines an elongated slot, and theactuating screw is pivotally connected to the link by a pin connected tothe actuating screw and projecting into the elongated slot, and whereinas the actuating support translates along the predetermined path, thepin translates within the elongated slot, and a height of the spacer isnot thereby substantially changed.
 8. The spacer of claim 1, the secondendplate having at least one ramped surface mateable with the at leastone ramped surface of the frame, whereby when the second endplate ismoved relative to the frame, the second endplate is moved in a directionaway from the frame to increase a height of the spacer.
 9. The spacer ofclaim 1, wherein the actuating screw defines a longitudinal axis, theactuating screw pivotable in connection with the link to form an anglebetween the actuating screw longitudinal axis and the longitudinal axisof the frame.
 10. The spacer of claim 1, wherein the link defines anelongated slot, and the actuating screw is pivotally coupled to the linkby a pin connected to the actuating screw and projecting into theelongated slot.
 11. The spacer of claim 1, wherein the endplate iscurved along a substantial portion of its length.
 12. The spacer ofclaim 1, wherein the nut is rotatable at a plurality of angularorientations between the actuating screw and the frame.
 13. The spacerof claim 1, wherein the first endplate and the frame form a slidingflanged connection therebetween.
 14. The spacer of claim 1, wherein theat least one ramped surface of the frame comprises at least two rampedsurfaces, and the at least one ramped surface of the first endplatemateable with at least one of the at least two ramped surfaces of theframe, whereby when the endplate is slideably moved by rotation of theactuating screw and movement of the link, the at least one firstendplate ramped surface slides against the at least one frame rampedsurface to cause the first endplate to move along an axis transverse tothe longitudinal axis to increase a height of the spacer.
 15. The spacerof claim 1, wherein the first endplate includes one or more projectionsconfigured to engage bone of the joint when the implant is positionedbetween bones of the joint.
 16. The spacer of claim 1, wherein the nutincludes a circumferential groove, and the actuating support includes acircumferential groove, the spacer further including a ring configuredto be positioned partially within both the nut groove and the actuatingsupport groove, to rotatably retain the nut in connection with theactuating support.
 17. A method of separating bones of a joint,comprising: inserting a spacer between bones of the joint, the spacerincluding a frame having a longitudinal axis and at least one rampedsurface; a first endplate configured to engage a first bone of thejoint, the first endplate having at least one ramped surface mateablewith the at least one ramped surface of the frame, whereby when thefirst endplate is moved relative to the frame in a direction along theframe longitudinal axis, the first endplate is moved in a direction awayfrom the frame to increase a height of the spacer; a second endplateconfigured to engage a second bone of the joint; a link moveable withrespect to the frame, the link having a projection engageable with thefirst endplate to thereby move the first endplate along the framelongitudinal axis when the link is moved with respect to the frame; anactuating screw moveable with respect to the frame and coupled to thelink to cause movement of the link when the actuating screw is movedwith respect to the frame; and a nut engaged with the actuating screw,the nut rotatable with respect to the frame to move the actuating screwwith respect to the frame.
 18. A spacer for separating bones of a joint,the spacer comprising: a frame having a longitudinal axis and at leastone ramped surface; a first endplate configured to engage a first boneof the joint, the first endplate having at least one ramped surfacemateable with the at least one ramped surface of the frame, whereby whenthe first endplate is moved relative to the frame in a direction alongthe frame longitudinal axis, the first endplate is moved in a directionaway from the frame to increase a height of the spacer; a secondendplate configured to engage a second bone of the joint; a linkmoveable with respect to the frame, the link having a projectionengageable with the first endplate to thereby move the first endplatealong the frame longitudinal axis when the link is moved with respect tothe frame; an actuating screw moveable with respect to the frame andpivotally connected to the link to cause movement of the link when theactuating screw is moved with respect to the frame; and an actuatingsupport slideably connected to the frame to be movable along apredetermined path.
 19. The spacer of claim 18, wherein the link definesan elongated slot, and the actuating screw is pivotally connected to thelink by a pin connected to the actuating screw and projecting into theelongated slot, and wherein as the actuating support translates alongthe predetermined path, the pin translates within the elongated slot,and a height of the spacer is not thereby substantially changed.